Generally, an electric parking brake (EPB) is a brake that is locked during stopping of a vehicle and is automatically unlocked when starting the vehicle. In other words, the electronic parking brake is locked even though a driver does not engage a brake pedal during a period in which the vehicle is stopped and is automatically unlocked when the driver engages only the brake pedal in the state in which the brake is locked when the vehicle starts, such that the vehicle starts as it is. Therefore, the electronic parking brake improves convenience of the driver on a slope (e.g., inclined road), when traffic congestion is severe, or the like.
The electronic parking brake generates appropriate target clamping force by pulling a brake wire through a brake operating motor based on a result obtained by synthesizing state information such as a load of the vehicle, a gradient of a parking place, and the like, and a driver's intention. In other words, target clamping force of the vehicle is determined based on tension of the brake wire that operates the brake, and a tension measuring sensor that senses the tension of the brake wire is used to determine whether the brake wire is pulled by appropriate tension through the brake operating motor.
The tension measuring sensor transfers the tension of the brake wire to a controller (an EPB, an electronic control unit (ECU), or the like) to allow the tension of the brake wire to be appropriately adjusted. Meanwhile, an advanced emergency brake system (AEBS) senses a possibility of collision with a preceding vehicle to provide a primary warning to the driver, and automatically decelerates the vehicle to avoid the collision with the preceding vehicle while providing a secondary warning for informing the driver of automatic braking when a reaction of the driver is not present or the collision is determined to be inevitable. Since the AEBS according to the related art operates a main brake to brake the vehicle, when maximum target clamping force of the main brake is insufficient, particularly, for a commercial vehicle, collision with the preceding vehicle may not be prevented.